1. Field of the Invention
The present invention generally relates to fine tuning of television (TV) broadcasting signals, and more particularly to an apparatus for finely adjusting tuning data for a TV receiver and the method thereof which can finely adjust the tuning data of a selected channel automatically and/or manually when especially a detuned broadcasting signal or a broadcasting signal having a strong/weak electric field is tuned, so that a user can enjoy a clear picture when selecting a channel. 2. Description of the Prior Art A conventional apparatus for finely adjusting tuning data for a TV receiver is shown in FIG. 1. The conventional apparatus comprises a microcomputer 1 for controlling the tuning of television broadcasting signals by outputting tuning data and for controlling the display of OSD (on-screen display) characters, a remote control receiver 2 for entering function key signals to the microcomputer 1, a key pad 3 for manually entering function key signals to the microcomputer 1, a tuner section 4 for selecting and tuning a channel broadcasting signal among channel broadcasting signals inputted through an antenna ANT in accordance with the tuning data inputted from the microcomputer 1, an intermediate frequency (IF) processing section 5 for IF-processing the output signal of the tuner section 4 and for detecting a sync signal and an automatic fine tuning(AFT) signal of the channel broadcasting signal to output the detected sync and AFT signals to the microcomputer 1, an image processing section 6 for processing an image signal outputted from the IF processing section 5, an OSD character generating section 7 for generating an OSD .character signal under the control of the microcomputer 1, and a mixing section 8 for mixing the output signals of the image processing section 6 and the OSD character generating section 7 to output the mixed signal to a color cathode-ray tube (CRT) 9.
The conventional apparatus as constructed above operates as follows:
When a channel selection key signal is entered to the microcomputer 1 by the user's manipulation of the remote control transmitter or of the key pad 3, the microcomputer 1 outputs to the tuner section 4 the tuning data of the channel selected according to the entered channel selection key signal. The tuner section 4 selects and tunes the channel broadcasting signal among the broadcasting signals received through the antenna in accordance with the tuning data inputted thereto, and then the IF processing section 5 processes the output signal of the tuner section 4. Also, the IF processing section 5 detects a sync signal from the output signal of the tuner section 4 and detects an AFT signal resulting from the tuned state. The detected sync signal and the AFT signal are inputted to the microcomputer 1.
The microcomputer 1 discriminates whether the channel broadcasting signal selected by the user has been tuned or not, depending on the sync signal inputted from the IF processing section 5. That is, if the sync signal is inputted, the microcomputer 1 discriminates if the broadcasting signal is accurately tuned, depending on the level of the AFT signal. If the level of the AFT signal deviates from a predetermined range of level the microcomputer 1 performs automatic fine adjustment operation by varying the tuning data outputted to the tuner section. 4.
The level of the AFT signal outputted from the IF processing section 5 varies according to the tuning state of the broadcasting signal. The microcomputer 1 recognizes that the selected broadcasting signal is accurately tuned when the level of the detected AFT signal is within a predetermined range of level, which centers the intermediate level of the AFT signal. When the level of the detected AFT signal deviates from the predetermined range, the microcomputer recognizes that the selected broadcasting signal is inaccurately tuned.
Meanwhile, in order to achieve an accurate tuning of the selected channel broadcasting signals, the microcomputer 1 performs a broadcasting signal search with respect to 3 divided search regions, i.e., a first search region of fo .+-.1 MHz, where fo is the center frequency of one broadcasting signal having a frequency band of 6 MHz, a second search region of (fo-1.5).+-.1 MHz, and a third search region of (fo+1.5).+-.1 MHz. That is, the microcomputer 1 outputs a phase locked loop (PLL) data as a tuning data for fo when firstly tuning the selected channel, and if the level of the AFT signal inputted to the microcomputer according to the tuning data for fo is not within a predetermined range of level, the microcomputer 1 performs a search operation by outputting tuning data within the first search region. If the level of the AFT signal is still not within the predetermined range until the search operation within the first search region has been completed, the microcomputer 1 then performs a search operation with respect to the second and third search regions in turn. If the AFT signal level is still not within the predetermined range until the search operation within the first to third search regions has been completed, the microcomputer 1 recognizes that the selected channel has no broadcasting signal and thus finishes the automatic fine adjustment operation after outputting the tuning data for fo.
The tuned broadcasting signal of the selected channel is inputted to the IF processing section 5 to be IF-processed, the image signal outputted from the IF processing section 5 is processed by the image processing section 6, and then the processed image signal is outputted to the mixing section 8. Meanwhile, the OSD character generating section 7 generates the OSD character signal under the control of the microcomputer 1 and the generated OSD character .signal is outputted to the mixing section 8 to be mixed with the image signal from the image processing section 6. The mixed image signal and the OSD character signal are then outputted to the CRT 9 to be displayed on its screen.
However, such a conventional apparatus for fine adjustment of tuning data suffers from the disadvantage in that, though an accurate tuning may be effected .when the broadcasting signal the selected channel is found within the first search region, flickering may occur in the picture during conversion of search region from the first search-region to the second search region and/or from the second search region to the third search region when the broadcasting signal is found within the second or third search region, because the fine adjustment of tuning data is performed by successively searching the broadcasting signal of the selected channel within the first to third search regions. Further, if the determination region of the AFT signal level is incorrectly adjusted even when the broadcasting signal is detected by the search operation, the broadcasting signal of the selected channel may not be accurately tuned, causing the picture quality to deteriorate, giving inconvenience to the user.